Plugs, balls, darts, etc. are used in the downhole drilling and completions industry for actuating of a variety of tools and assemblies. Typically, the plugs land in a seat, blocking fluid flow through a passage and enabling a differential pressure to be created thereacross for actuating a tool or assembly. After actuation of the tool or assembly, it is often desirable to remove the resulting obstruction. Advances in selectively removable plugs and plug seats are accordingly well received by the industry.